Law enforcement groups and family members of victims of December's San Bernardino mass shooting have backed the FBI and opposed Apple in the court fight over an iPhone used by one of the shooters.

Family members of the shooting victims "seek to remind all parties of the terrible crime -- an act of terrorism -- the United States must investigate to its fullest," wrote lawyers for family members of five victims and one witness to the shooting. "Ultimately, this is a situation where no stone can be left unturned."

Much of the debate over the FBI's demands of Apple assistance has focused on the "potentially global ramifications" of Magistrate Judge Sheri Pym's Feb. 16 order requiring Apple to comply, but there's a law enforcement investigation to consider, the lawyers added.

Dozens of tech companies and privacy groups filed briefs in support of Apple, as Pym weighs the arguments related to the FBI's demand that Apple assist it with the unlocking of one of the shooter's iPhones. The husband of one shooting victim who survived has also voiced support for Apple's position.

But the opinions expressed in amicus briefs filed to meet Pym's Thursday night deadline were far from unanimous.

Among the groups filing briefs in support of the FBI were the Federal Law Enforcement Officers Association (FLEOA), the Association of Prosecuting Attorneys (APA), the National Sheriffs' Association, the California State Sheriffs' Association, the California Police Chiefs' Association, and the California Peace Officers' Association. Another brief in support of the FBI came from the San Bernardino County District Attorney's Office, the prosecutor in the country where the shooting took place.

"In order to fulfill their duties [law enforcement agencies] must have access to all reasonable means of procuring relevant evidence," wrote lawyers for the FLEOA, the APA and the National Sheriffs' Association. "In this digital age, data stored on mobile devices has proven time and again to be critical in assisting law enforcement officers to do their jobs."

Apple has taken a "dangerous" position in the case, the lawyers added. "Apple's refusal to provide assistance has far-reaching public safety ramifications by making it difficult, and in some cases impossible, for law enforcement to fulfill its obligation to investigate crimes, protect the public by bringing criminals to justice, and enforce the law."

Among the companies and groups filing briefs in support of Apple are Google, Microsoft, Facebook, Amazon, Cisco Systems, LinkedIn, eBay, Kickstarter and Reddit. Also supporting Apple's position are the Electronic Frontier Foundation, the Electronic Privacy Information Center, Consumer Action, the Center for Democracy and Technology, the American Civil Liberties Union, 32 law professors and 46 technologists, researchers and cyptographers.

The court and the FBI are attempting to reinterpret a 227-year-old law called the All Writs Act to give the government "an open-ended source of new powers," wrote lawyers representing Google, Microsoft, Facebook, Amazon and other companies.

The All Writs Act allows courts to "issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law." However, the FBI is asking the court to "endorse an unprecedented expansion of the act that would allow law enforcement to force private companies to circumvent security features that protect their customers' most sensitive information from hackers and criminals," according to the lawyers representing the tech companies.

At the request of the FBI, Pym ordered Apple to write new source code to defeat a password protection feature on an iPhone used by San Bernardino mass shooter Syed Rizwan Farook. The FBI wants Apple to disable the phone's security feature that erases its contents after 10 wrong password attempts and also to defeat the phone's time delay between password-entering attempts.

Without those security protections in place, the FBI could enter an unlimited number of passwords in a brute force attack and gain entry into the phone in a matter of hours.